One of the lesser known works by the author, this book intrigued me because it is based more in the digital world of computers, cryptography, and the NSA. Perhaps not as compelling of a story as his other works, but I enjoyed it for its realism in the secret world of data encryption and espionage. I also seem to recall a reference to the "Kryptos" sculpture at CIA headquarters by Jim Sanborn, but I cannot find a citation, so I may be confusing this with another book.